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'Weekend Smog' as Part of the Bigger Picture

June 01, 2004

Re "As Smog Thickens So Does the Debate," May 24: Your story on "weekend smog" missed several key points. Ozone smog is not our only air-quality problem. Fine-particulate pollution, also known as PM2.5, creates hazy vistas and is an equal if not greater threat to health. It has been linked to a wide range of health effects from increased hospital admissions to early deaths. Since a major portion of PM2.5 is composed of nitrogen compounds, we cannot reduce PM2.5 levels without reducing nitrogen-oxide emissions.

Although weekend ozone levels for the last 35 years have been as high as or higher than the levels on weekdays, weekend air quality has improved significantly, at nearly the same rate as that during weekdays. Last summer was a notable exception, primarily because the weather was hotter and more stagnant than it has been for years, resulting in a higher number of smoggy days on weekdays and weekends.

Following the recommendation of auto manufacturers and a few scientists to slow down nitrogen-oxide emission reductions will not significantly benefit ozone air quality and would delay reductions in PM2.5 pollution. That could mean additional smog-related illnesses and deaths.

Barry R. Wallerstein

Executive Officer

South Coast Air Quality

Management District

Diamond Bar

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